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750 Breva Engine noise

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rapheal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 18 Dec 2018 at 21:59
if road dirt gets into the clutch pushrod that can make an awful noise when the bearing fails
Antonio strips and greases mine on the big service at the same time as the operating arm pivots
the bearing can seize through lack of use, or idiots using a pressure washer on the machine
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 18 Dec 2018 at 22:05
True, Guzzis are not sealed against pressure washers.

Brian.

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NevilleG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NevilleG Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 2018 at 11:23
Originally posted by Roadrunner Roadrunner wrote:


Hi could you put a video up of your current bike 😊


I don't think there would be much point in doing that because, as I have explained before, it doesn't make that horrible twittering screeching noise (I wouldn't even consider riding it if it did !) and the knocking noise, although present, is nothing like as loud.
I have decided to just keep an eye (ear !) to it and tear the engine/gearbox apart if it gets worse.
One thing that has been mentioned, by Raphael I think, concerning the push rod and cup is another possibility, if the push rod, which runs through a hole in the gearbox input shaft and onto the centre of the cup, is lacking lubrication or a bit corroded. Can that be accessed without taking the gearbox off ? Hmmm !
Nev.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote George S Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 2018 at 12:07
I believe that that push rod and thrust bearing pulls out from rear of gearbox. It does on earlier models. Maybe have to remove swingarm. Thinking about it I would check thrust bearing and rod first.
George

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 2018 at 16:53
Yes the thust bearing is pressed into the rear cover of the gearbox from the outside.
But you have to remove the swinging arm to get at it.
Brian.

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rapheal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 2018 at 22:52
useful tip from my mechanic ( not me I use a hammer on everything)
when you remove the rear wheel, put a wooden block or an axle stand under the swing arm
otherwise when you undo the shock absorbers it will droop down and the front will contact the gear linkage and bend the short operating arm or even snap it 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 20 Dec 2018 at 09:21
Good tip, and it's heavy with the bevel drive attached.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote NevilleG Quote  Post ReplyReply Direct Link To This Post Posted: 20 Dec 2018 at 09:59
Thanks Guys, I was planning to take the bevel box and swing arm off in the Spring anyway, to re-paint them. Nev.
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rapheal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 21 Dec 2018 at 23:20
Originally posted by NevilleG NevilleG wrote:

Thanks Guys, I was planning to take the bevel box and swing arm off in the Spring anyway, to re-paint them. Nev.

I engraved the reg no on mine while Antonio had it out
if it ever gets nicked its a quick way to prove its mine
before I bash some ones head into it !!
I also did the wheels and lots of other bits
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Post Options Post Options   Thanks (1) Thanks(1)   Quote NevilleG Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2019 at 12:42
For those who might still be interested, over the last couple of months I have been stripping the engine apart and,essentially, found very little wrong with it.
After all the input from various contributors and my own thoughts on the cause, I concentrated on the clutch assembly and crankshaft, but checked out all the other parts associated with the clutch operation as well, including fitting a new clutch release bearing.
At 17368 miles, I found the clutch was all in perfect condition and the only thing that I could find wrong with the crankshaft assembly was some uneven wear on the rearmost half thrust washer. The design of how this half washer is located and retained can possibly lead to a build-up of oil-borne debris behind it through a small oil passage, which I believe had moved it rearwards and caused some wear at that point. This could also reduce crankshaft end-float.
With new thrust washers fitted, crankshaft end-float measured up at 5-thou and I decided to use Loctite 603 to fix them against their locating faces to prevent any future lateral movement.
The crankshaft main bearing shells and journals were unmarked and had no measurable wear, however it was surprising to find how much running clearance Guzzi give the crankshaft. With no oil film, there is much more movement than I would have expected, but I had no means of accurately measuring what it was.

After reassembling and refitting the engine, the noise is still there and so my conclusion is that when the oil is hot and thinned down, the end force applied to the crankshaft upsets its balance sufficiently to allow it to float in the vertical plane of the main bearing clearance. When the engine is cold, the oil is thick enough to provide a better cushioning effect and reduce the movement.

The main bearing clearance is probably more suited to the age of thicker Mineral oil, despite Guzzi recommending modern fully synthetic grade, but a brief experiment recently with some "Elf 20w/50 motorcycle" mineral oil made no improvement and "Duckhams 20w/50" of the 1960's is sadly no longer available.

No doubt my bike will run on happily and reliably for many more miles, but it's annoying to have to put up with something like this that just doesn't seem right somehow.   NEV.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mr Grumpy Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2019 at 13:27
So it is part of the character then.

I've changed all the oils on my B750 this week. It doesn't seem to have made any difference to the way the bike sounds.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nab301 Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2019 at 20:26
Originally posted by NevilleG NevilleG wrote:

For those who might still be interested,   NEV.

Thanks for posting  , Interesting  findings..
Nigel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 11 Apr 2019 at 20:27
I suspect the noise comes from the gearbox input shaft.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote NevilleG Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 2019 at 13:45
Originally posted by Brian UK Brian UK wrote:

I suspect the noise comes from the gearbox input shaft.


I don't think you've thought that through Brian !

The clutch operating rod passes down the middle of the gearbox input shaft and pushes the pressure plate away from the friction plate. The friction plate, which is mounted on the splines of the gearbox input shaft, then stops rotating, as does the gearbox input shaft.
If it isn't rotating and has no other force acting on it, how can it be making any noise ???
I checked the gearbox input shaft bearing, which was perfect, but fitted a new clutch thrust race, which is under load and could have been the culprit, as a matter of course. Nev.
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rapheal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 1 hour 43 minutes ago at 20:33
my one sounds like a bag of spanners some days
I took sage advice from the late Ken Craven
stop worrying about it 
unless it gets worse

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